Thanks to egrep for linguists for giving this nice and clear example of using egrep.

There are different ways to match both star and stars within a single search pattern. The most straightforward way might be to tell egrep to look for either the string star or the string stars with the help of a disjunction, expressed with the vertical bar, |. This time the search pattern has to be quoted in order for the program to know where the search pattern starts and ends

    $ egrep -w 'star|stars' sonnets.txt
    Not from the stars do I my judgement pluck,
    And constant stars in them I read such art
    Whereon the stars in secret influence comment.
    Let those who are in favour with their stars,
    Till whatsoever star that guides my moving,